


Kinktober 2017

by Shadow_of_Quill



Category: Undertale (Video Game)
Genre: Aphrodesiacs, Begging, Biting, Bondage, Emotional Abuse, Flamebros, Forniphilia, Incest, M/M, Masochism, Mythfell, Oviposition, Rape, Rimming, Species Swap, Swapfell, Underfell, Vampirism, Xeno, proto!skelebros, reborntale
Language: English
Status: In-Progress
Published: 2017-10-06
Updated: 2018-12-11
Packaged: 2019-01-09 03:44:49
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 9
Words: 8,003
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12268200
Author URL: https://archiveofourown.org/users/Shadow_of_Quill/pseuds/Shadow_of_Quill
Summary: Set of ficlets for the Kinktober 2017 promptlist.





	1. Index

**Chapter 1: Index**

Unless specifically noted, none of these fics are meant to be describing the same relationship.  
This index will likely end up not being up-to-date.

**Chapter 2: Prompt: Aphrodesiacs**  
_Papyrus/Sans, Underfell, first time, dubcon, implied/referenced offscreen non-consensual drugging, incest_  
Papyrus makes a bold choice to get Undyne and Alphys to stop mooning over each other, and then has to face the consequences.

**Chapter 3: Prompt: Human Furniture**  
_Sans/Papyrus, Swapfell, established relationship, no sex, on display, implied incest_  
Sans decided to show Alphys his prized possessions.

 **Chapter 4: Prompt: Biting(/Vampirism)**  
_Papyrus/Sans, Underfell, Dom/sub tones, established relationship, implied incest_  
Short introspective piece.

**Chapter 5: Prompt: Oviposition**  
_Papyrus, hinted Sans/Papyrus, Mythfell, no sex, willing sort-of cannibalism?, not-really-sexual relationship, hinted incest between adopted siblings_  
Papyrus _hated_ breeding season.

**Chapter 6: Prompt: Begging(/Masochism)**  
_Sans/Papyrus, nonstandard Reborntale (demon!Papyrus, angel!Sans), no sex, masochist!Papyrus_  
Angels can purify demons. Papyrus asked Sans to purify him.

 **Chapter 7: Prompt: Prostitution(/Sexual Slavery)**  
_Papyrus/Sans, Papyrus/other, alternate universe, institutionalised sexual slavery/prostitution/rape, rape as public entertainment, incest, darkfic_  
In this world, it's fuck or be fucked. Papyrus will do whatever it takes to keep himself and brother safe.

 **Chapter 8: Prompt: Rimming**  
_Papyrus/Sans, proto!skelebros, rape shading to dubcon, incest, internalised victim-blaming/slut-shaming, emotionally abusive relationship, bondage, denial, first time, darkfic_  
Maybe Sans should have paid more attention to what he was teaching Papyrus about sexual relationships _before_ he found himself tied to a table.

 **Chapter 9: Prompt: Xeno**  
_Sans/Papyrus, speciesswap, flamebros, incest, underage (exact ages unspecified), accidental first time, mutual lack of understanding of what they're doing till afterwards, non-humanlike sex, monsters do not have human cultural values_  
They're the only fire elementals they know. Shouldn't they know how to kiss?


	2. Aphrodesiacs

**Notes for the Chapter:**

> _Papyrus/Sans, Underfell, first time, dubcon, implied/referenced offscreen non-consensual drugging, incest_

Papyrus snarls as the view in front of him wavers. It's nothing he wasn't prepared for, nothing he can't handle - The Great and Terrible Papyrus will _not_ be taken down by a simple drug!

Or even a complicated drug, which is more likely considering what this is - he shakes the thought away, and fights not to lose his balance as the world tilts alarmingly.

It's possible that his spur of the moment decision _might_ have been a _little_ hasty. But he's just so _tired_ of watching Undyne and Alphys dance around each other like this - Undyne cooked Alphys a special dinner, Alphys suspected it was poisoned. Alphys invited Undyne to watch anime, Undyne panicked and accused her of putting in brainwashing subliminals. Undyne tried to give Alphys a private concert, Alphys decided she was going to be garroted with a piano wire (something Papyrus has never had explained to him, and he really wants an explanation someday) - so when Alphys sent over a bottle of wine that even Papyrus could tell had been 'treated' and Undyne started working herself into a fit of paranoia, drinking a glass to show her that it was fine had seemed like the best thing to do.

His swift thinking did convince Undyne to drink the rest of the bottle, and he ran into Alphys as he left, so he's confident that his intervention will lead to the long-awaited resolution of the Underground's most notorious crossed-wires potential relationship.

Unfortunately, it's also leading to him losing his mind from Alphys' best-quality aphrodesiac. Forget his duties and the puzzle he'd meant to work on; the state that he's in, he has a horrible suspicion that he'd spread his legs for _Jerry_ if the asshole came across him and thought to ask. Or tell. Or command - he yanks his mind away from that line of thought and hurries on. The house will be empty for hours, Sans running low-grade scams at his post and then heading straight to Grillby's.

There'll be more than enough time for Papyrus to take himself in hand - to handle the issue - _Fuck_ it! He snarls, and picks up speed. His house. His room. His bed.

And _then_ he can use his fingers.

He doesn't recognise the flaw in his plan until he slams the front door shut behind him, scrabbling desperately at his breastplate to get it off, off, he needs it off, he needs everything off _now_ \- and Sans pops out of his room, looking startled and possibly a little guilty.

"boss?"

Of _course_ Sans isn't at his post, snarls the rapidly-shrinking coherent part of Papyrus' mind. It's not as if he can afford to risk losing consciousness there, and with his shortcuts, why _wouldn't_ he come back to their house for an illicit nap?

The rest of him is too busy taking in Sans' (vulnerable) expression and (invitingly) dishevelled clothing to feel properly aggravated. He takes a step towards him, reaches out -

 _No, no, no, this is **wrong** ,_ his mind shouts, _this is his **older brother** who's never shown the slightest interest in this with him!_ He jerks to a halt, trembling, caught between his need for sex and his need to not hurt his brother.

Sans walks closer, because he's always combined being one of the smartest monsters Papyrus knows with being one of the biggest idiots. "boss? you okay?"

Papyrus keens, wanting Sans to touch him, knowing that he shouldn't. He wavers between stepping forward and stepping back, scrabbling to hold on to the fact that Sans is _not willing_ and force it to counterbalance how very much _Papyrus is._

Sans stops, maybe because of the sound Papyrus is making, maybe because he's just noticed the glow of Papyrus' magic gathering around his pelvis and ribcage. Papyrus can see him adding things up, working out what led to this -

Sans looks sick, furious. "someone dosed ya?" It's close enough to the truth. Papyrus nods. "shiiit." Sans reaches up, claws almost digging into his skull before he diverts into tugging at his collar. "okay. okay. we can work with this. just gotta find you someone you want -"

Papyrus lights up - is this permission? Sans notices. "got someone in mind?" he asks, trying to smile for Papyrus but tense with the need to do something.

Papyrus nods violently. "YOU."

Sans freezes, stares at him, sockets getting wider as he blushes till his face is the same shade as his jacket. "me?" he squeaks. "whah?"

Papyrus watches expectantly for him to say yes or no. Instead, he repeats, "you want _me?"_ as if it's incomprehensible.

"I WANT YOU." Papyrus takes a step forwards, forgets why he was holding still. "I WANT YOU," eyelights fixing on the collar he let Papyrus give him, on the fragile vertebrae it encircles, on the collarbones below them showing through the open neck of his shirt, "I WANT YOU," as his hands rise to push Sans' unfastened coat off his shoulders -

"Stop!"

Papyrus freezes in place, and it hurts, it _hurts_ to have Sans so close and not be touching him, but Sans said no.

Sans said no.

Papyrus collapses in on himself, magic rebelling as that thought penetrates the haze in his mind. Sans said no, Sans doesn't want this, he was going to touch Sans and Sans doesn't want this, he'd have _hurt_ Sans and _he's_ hurting but _he can't hurt Sans!_

Sans moves and Papyrus scrambles backwards, he can't touch Sans, he can't hurt Sans, he _can't_ and he _hurts,_ he hurts so much, he wants - he can't -

Sans sounds worried, Papyrus is scaring him. "boss," he says, "paps," he says, and Papyrus' magic is aching and needy in his pelvis, around his soul, and he meets his brother's eyelights and whimpers, lying back, femurs spread, offering himself despite knowing Sans doesn't want him -

But Sans reaches for him, face soft with wonder. Sans leans over him and touches him, Sans fingerfucks his pussy into existence and kisses him while he does it, Sans touches him and opens him and then he's arching and crying out as Sans _fills_ him and makes him stop hurting.

Sans draws back - Papyrus whines - Sans thrusts in again and Papyrus groans, wraps himself around Sans and tries to pull him closer, deeper, soul pressing so tightly against his brother's it's as if they're trying to merge, and Papyrus' soul is leaking pleasure but so is Sans', he's enjoying this, he _wants_ this, and that's the thought that sets off Papyrus' first orgasm.

"fuck, you're beautiful," Sans whispers, and Papyrus comes again just from hearing him say it. "you-! fuck! Paps - _sweetheart_ -"

Papyrus meets his eyelights, dizzy and scared of how out-of-control he is, and Sans says helplessly, "you're so _perfect."_

 

By the time the drug finally wears off they're both too exhausted to do more than curl around each other on the floor. "who drugged ya, anyway?" Sans asks, arms tightening protectively.

Papyrus growls, embarrassed that he's going to have to explain what happened. "IT WAS THE BEST WAY TO GET UNDYNE TO ACCEPT ALPHYS' PRESENT," he grumbles.

Sans stares at him, working out what happened from that one sentence. "what, making yourself collateral damage?"

"IT'LL BE WORTH IT IF IT STOPS OUR TRAINING SESSIONS BEING INTERRUPTED BY HER RANTS ABOUT HOW MUCH SHE WANTS TO KNOW WHAT LIZARD COOCH IS LIKE!" Papyrus insists.

Sans stares at him in disbelief, then shakes his head. "you say so, boss." There's an awkward pause before he blurts out, "so our being - us becoming lovers, that's not good enough for it to be worth it?"

The words are a reassurance Papyrus hadn't known he needed - Sans wants this, with him, to be a permanent thing instead of a drug-induced madness. 

It almost makes up for how stupid the question Sans just asked is.

"I DIDN'T KNOW THIS WAS AN OPTION WHEN I CHOSE TO TAKE THE DRUG, OR I WOULDN'T HAVE NEEDED THE DRUG TO START THIS IN THE FIRST PLACE," Papyrus explains, reminded again of his brother's combination of intelligence and idiocy. "AND YES, THE DRUG WOULD BE WORTH IT EVEN IF THIS WAS THE ONLY RESULT."

 

It's just as well he decides that.

"PLEASE, BY ALL THAT IS HOLY, LET ME GO ONE. DAY. _WITHOUT_ HEARING ABOUT WHAT YOUR GIRLFRIEND CAN DO WITH HER TONGUE. I AM _BEGGING_ YOU, HERE."

Undyne smirks. "What, after you went through so much trouble to get us together? Nah. And seriously, when she curls it _just right..."_


	3. Forniphilia

**Notes for the Chapter:**

> _Sans/Papyrus, Swapfell, established relationship, no sex, on display, implied incest_

Sans tapped his fingers against his teeth. Alphys was coming over to view his most valuable treasures. He needed to display them all to the best possible advantage...

His eyes fixed on Papyrus, and he nodded slowly.

"milord?"

"STRIP, MUTT," he ordered. Papyrus obeyed immediately, folding his clothes neatly and piling them beside him on the floor. Sans looked him over, and smirked. "I NEED A TABLE TO DISPLAY MY TREASURES TO ALPHYS."

Papyrus' sockets widened in understanding. "i live to serve you, milord," he said.

"OF COURSE YOU DO." Sans waved a hand dismissively. "I THINK THE GLASS TOP, FOR THIS."

The glass tabletop was a thick sheet of glass, slightly longer than Papyrus was tall. Papyrus collected it from the closet it was stored in as Sans cleared an area of the floor, then handed it over to his Lord and got into position.

It had taken quite a bit of experimentation with planks to learn how to do this, but they were both well-practised by now. Papyrus lay down and arranged himself, hands and knees raised to equal heights, and then his Lord set the tabletop in place and tested whether it was truly level.

"ACCEPTABLE," he said, and Papyrus felt a warm glow from hearing that he'd succeeded on the first try. He watched with interest as his Lord laid out some of his more prized weapons and equipment, making a note of what Sans considered valuable enough to show off.

He felt his soul warm when he recognised some of them as things he'd found or made for his Lord - a knife sharpener, a set of throwing knives and holsters, an electrified baton.

Sans looked at him through the tabletop, eyelights sharp. "YOU'D BETTER NOT EMBARRASS ME, MUTT. ALPHYS IS NOT TO WITNESS YOUR FILTHY OVEREXCITEMENT, AM I UNDERSTOOD?"

Papyrus didn't nod. Furniture wasn't supposed to move. But it made him feel warmer to know that his Lord wanted to hoard his sexual uses away to enjoy privately, instead of sharing them in some attempt to curry favour.

Sans arranged and rearranged the items he'd selected, trying to find the best layout to show them to advantage. Papyrus watched, mind blank, content to know that he was useful.

Sans had just stepped back to consider the latest arrangement when Alphys pounded on the door. _"Get out here, pipsqueak!!"_

Sans huffed and turned on his heel to let her in, leaving Papyrus to realise for what felt like the first time that someone else was going to see him as a table-base. The thought sent a shiver of excitement through his magic, and he focussed on holding the tabletop absolutely steady and not letting his magic pool and form. He could feel it flowing around his bones, but he knew that would be fine, so long as it wasn't visible.

"Come on, then! Let's see what's -" Alphys cut herself off as she reached the doorway and saw the display Sans had arranged. "The _fuck?"_

Papyrus didn't let himself smirk at her confusion, watching from his peripheral vision as she blatantly stared at him. He didn't let his pussy form either, despite the flowing heat that told him he'd be soaking wet if he did.

"What, you were expecting bonus points for originality?" Alphys got out, trying to regain any ground she'd lost in her suprise.

Sans arched his orbital ridges at her. "WHAT DO YOU MEAN? YOU'RE THE ONE WHO ASKED TO SEE ALL MY MOST USEFUL PIECES OF EQUIPMENT."

Papyrus lay still, to all appearances completely unaware of the conversation happening next to him. Smug warmth at his Lord's words filled him, together with a sharp amusement at Alphys' confusion.

If he'd been stood beside the rest of his Lord's armory, Alphys might have realised that he was meant to be part of it. As it was, his Lord could truthfully state that he'd shown Alphys everything he most valued - and if she didn't recognise that Papyrus was one of those things, well, that was her problem, wasn't it?


	4. Biting (Vampirism)

**Notes for the Chapter:**

> _Papyrus/Sans, Underfell, Dom/sub tones, established relationship, implied incest_
> 
> This is tiny.

They don't talk about it.

They talk about the other things - the bindings, the insults, the fists and claws - but not the teeth.

They talk about how Sans needs to pretend to fight back, but not about how Papyrus needs to taste his marrow.

They talk about how Papyrus needs to _know_ that he has Sans pinned exactly where he wants him, but not about how Sans needs to feel his bones pierced so his marrow drips out.

They talk about what feels good and what feels bad. They talk about where their tastes mesh and where they grate, and find and make common ground to satisfy them both.

They don't talk about Papyrus biting Sans and nursing at the wounds. That's different - that's necessity, not pleasure, and has been since that experiment to improve Papyrus' fighting abilities went so terribly wrong...

And if there's a pleasure in it that laid the grounds for all the pleasures they _do_ talk about, well, neither of them needs to admit that.

So long as they don't talk about it.


	5. Oviposition

**Notes for the Chapter:**

> _Papyrus, hinted Sans/Papyrus, Mythfell, no sex, willing sort-of cannibalism? (eating own unfertilised egg), not-really-sexual relationship, hinted incest between adopted siblings_
> 
> Mythfell is from [Mythtale](https://melle-d.tumblr.com/tagged/mythtale) by Melle-d.

Papyrus groaned, hands resting on his swollen belly. He _hated_ breeding season. The only good thing about it was that it didn't catch him off-guard (except for the first time, which had led to The Incident Which Was Not To Be Spoken Of). He could feel himself getting more possessive and territorial as it approached, and he took that as a warning and fled - _relocated_ until it wore off.

Unfortunately, he hadn't learned to recognise those warning signs till _after_ The Incident, which left his instincts making some very faulty assumptions.

It was bad enough that his instincts had locked on to that fat noodle as his mate, but to make matters worse, The Incident had led to Sans being uncommonly dominant - which Papyrus' instinctive magic was far too willing to accommodate.

He groaned again, shifting in the nest he'd half-heartedly built. He hated being egg-heavy like this, he hated the mindless push of his instincts to find his mate ( _any_ mate) to fertilise his egg, he hated almost everything about breeding season and the one part he didn't hate was utterly humiliating.

And was about to happen.

His insides clenched, relaxed, clenched, sending ripples of shameful pleasure through him as he started laying. His egg was a solid weight, slowly forcing him open, and the stretch and strain in muscles he normally didn't have was bizarrely sexual. He whined and panted, claws digging into his nest, no longer thinking about how embarrassing this was or how much it tore at his pride to be so undignified - not thinking about much of anything except the ache and satisfaction as his egg slipped down, and down, and _out..._

Papyrus collapsed on his nest as he shuddered through the aftershocks of his orgasm. The egg underneath him felt empty to his magic, devoid of the potential life that should have been inside it.

He paused to gather his strength before tearing the useless nest to shreds and picking up the worthless egg. The whole sordid episode was finished, and his instincts wouldn't push him to anything if he was around Sans now.

That lazy noodle had probably slept through the whole time Papyrus was away, he thought with a haughty sniff. No matter! Papyrus knew how to wake him up. Cooking something where he could smell it was all it would take.

And Sans was quite fond of scrambled eggs.


	6. Chapter 6

**Notes for the Chapter:**

> _Sans/Papyrus, nonstandard Reborntale (demon!Papyrus, angel!Sans), no sex, masochist!Papyrus_

"you sure about this?" Sans checked, wings fluttering nervously as he rocked on his feet.

Papyrus nodded, eyesockets wide and guileless in an expression that probably should have looked out-of-place on an ascended demon. "YES, VERY! PLEASE?"

For a moment, it seemed like that would be enough - but then Sans' gaze dropped to the marks on Papyrus' fingers, the brighter patch where Sans' halo came into contact with unpurified bone and - purified it. "you're _really_ sure?" he asked, reminded again of the scream of pain, the hurt and betrayal Papyrus had shown when it happened.

_"YES,_ I'M SURE!" Papyrus crouched to stare him in the face, tattered wings pooling on the floor around him like an old, ragged cape. "ASRIEL SAID I CAN BECOME AN ANGEL, LIKE YOU, BUT IT'S TAKING TOO LONG TO DO IT THE OTHER WAY. AND I DON'T WANT TO RISK MAKING YOU FALL INSTEAD," he added, voice dropping.

Sans grimaced. Asriel had explained a lot to them - what they were, what that meant, what could happen to them and what they could become - but part of Sans didn't want to trust him, and he had no idea why. Maybe it was the hint of personal experience when he warned them that even ascended demons could lead angels to fall. Maybe it was the wistful nostalgia on his face when he watched them together.

Maybe it was as simple as jealousy over how easily Papyrus believed him, when _Sans'_ words were picked apart and doubted (and alright, he hadn't been completely honest when he said that there was no pity involved in his decision to befriend Papyrus, but he'd existed for less than an hour at the time! He hadn't had time to learn just how worthwhile Papyrus was).

"PLEASE, SANS." Papyrus gave him a look of silent desperation, as if Sans was refusing to give him something he needed. _"PLEASE."_

 

_"PLEASE,"_ Papyrus said, watching for the telltale signs that Sans was giving in. He'd noticed that his angel was weak to his begging, and did his best not to use that against him - but this was in Sans' best interests! They could burn the evil out of Papyrus, and then he wouldn't be driven to say and do those things that hurt Sans, that made him go sad and quiet - or worse, smile and pretend that he was fine, that Papyrus hadn't hurt him at all. Papyrus hated that, because the worst parts of him always pushed him to accept it, to (pretend he) believe(d) it, to try and make Sans stew in despair and shame and guilt the way Papyrus did...

Papyrus could be _good_ for Sans.

Papyrus _wanted_ to be good for Sans.

And if Sans would just agree to use his own angelic nature to burn away the impurities in Papyrus, Papyrus could be sure that he _would_ be good for Sans, the way he wanted to be. _"PLEASE,"_ he repeated, and Sans finally gave in.

"youll say if you change your mind, right?"

"I PROMISE," Papyrus agreed immediately. He knew how much weight Sans attached to promises, even if neither of them knew why.

Sans twitched at the words, but he nodded. "okay." He rubbed his hands together, concentrating. "okay," he repeated as the blinding glow of holy magic (so different from the blue they could both use) started to build between them.

When his hands were fully coated, Sans reached out. Papyrus offered his own hands eagerly, biting back a whine as Sans' magic touched him. It hurt just as much as he remembered from touching Sans' halo, but things were different now. This wasn't something unexplained that he could only interpret as an undeserved attack, this was something he'd asked for, something that he wanted. Something that was good for him.

Papyrus watched avidly, ignoring the agony from being _changed_ as his phalanges whitened, soul soaring at the proof that this was working. "YES!" 

Sans offered him a smile, still not quite sure about what they were doing even as his hands slid up past Papyrus' wrists. Papyrus gritted his teeth, leaning in to the cleansing pain, relishing how the first sharp blaze faded into a comforting warmth and wanting more of that, "MORE, SANS, MORE, PLEASE!"

"okay," Sans murmured soothingly as he massaged the blissful agony into Papyrus' bones. "it's okay, i've got you." Papyrus shuddered, whining, trying to rub himself against the fire that brought that wonderful pain. "PLEASE, PLEASE, SANS, PLEASE, I WANT IT, PLEEEEEEASE!" the word became a drawn-out wail as Sans, sockets wide, brought his hands up and let his holy fire stroke along the membranes of Papyrus' wings.

The pain was so strong it took Papyrus' breath for a moment, and then he was babbling, "YESYESYESPLEASEPLEASEPLEASEPLEASEPLEASEPLEASEPLEASE PLEASE _MORE!"_

"sorry," Sans gasped, and Papyrus' sockets flew open (when had he closed them?).

Sans was drooping before him, utterly worn out as the last of the holy fire in his palms sputtered and died. "think that's as much as i can do for now."

Papyrus didn't think, just caught Sans up in a hug (the first one he'd managed without having to concentrate on not crushing or smothering his angel) and wrapped his wings around them both, unconsciously protective. "THANK YOU, THANK YOU FOR THIS, THANK YOU SO MUCH," he said, knowing the words didn't get across the tiniest portion of how grateful he was.

"heh, s'okay." Sans snuggled closer, trusting in a way that Papyrus felt he might finally deserve. "maybe i'll be up to more in a few days?"

 

"maybe i'll be up to more in a few days?" Sans offered. He hadn't expected Papyrus to be so into what must have been a very painful experience, but it was good to know that he hadn't damaged or broken their friendship.

Papyrus looked at him, sparkles of delight glittering in his sockets. "PLEASE?"


	7. Prostitution(/Sexual Slavery)

**Notes for the Chapter:**

> _Papyrus/Sans, Papyrus/other, alternate universe, institutionalised sexual slavery/prostitution/rape, rape as public entertainment, incest, darkfic_

There has never been a War between humans and monsters. Officially.

Humans rule the world, their souls so strong it's whispered that even a child could kill hundreds of monsters if it chose to. Monsters are used for their entertainment, competing with each other in sexual 'battles' where the winner is the last to climax, the losers' magic flaring from their souls in blazing auroras which are impossible to miss or hide.

Most monster children grow up in the orphanages, supported and overseen by humans, where they're taught their place in the world and trained to respond as the humans think they should - not while they're still in striped shirts, of course, but the moment they're old enough to leave childhood outfits behind they're expected to display themselves for the observers who come every month or so to 'bear witness', and from there they try to find human patrons to support them as they battle (because the monsters can _earn_ money, this one way, but they aren't allowed to _own_ it - that money belongs to the humans who own _them,_ and it's those humans who decide how much of it is spent on the wellbeing and comfort of the ones who earned it).

There are rumours and whispers of some rare monster couples earning enough favour to raise their own children, but no one suggests it ever makes a difference to those children's eventual fate.

And, of course, there are monsters who don't - or can't - participate in the 'battles'. The ones the humans admit to and care for despite their lack of use are shown off as great demonstrations of charity, pitied and worthless. The ones they don't - and there are many they don't - are left to survive as best they can without food or money, in a world where the shopkeepers refuse to sell to them because everything of any value (including money itself) is assumed to rightfully belong to a human.

Monsters are either whores, who belong to a human, or thieves, who don't - and humans are deadly cruel to thieves. 

Better to be a whore, and hope for an owner - a sponsor or a patron - who'll protect you, than to be a thief at risk of dying at the hands of any human who decides they want to kill you. So monster children appear at the orphanages, and the orphanages take them in and raise them to be sexual combatants, entering them in the battle system as soon as they're old enough. (As soon as they can pass for old enough, it's hinted, but how can you tell with creatures that age so unpredictably?)

Sans and Papyrus don't come from an orphanage to give them entry to the system. They aren't sure _where_ they come from, orphanage or thieves, but Sans is confident he knows why they're alone.

Sans is fragile, so fragile one touch with intent to harm could turn him to dust. No one would waste time training that. (Papyrus is younger; they might have thought he'd turn out the same, or he might have simply refused to let Sans go alone; he's stronger-willed than almost anyone Sans has ever met.)

Sans can't compete. Papyrus can.

Papyrus decided, years ago while they were stealing from shops and running from humans and hiding from everyone, that he _would_ compete.

Competing requires training and practise. Neither of them remember whose idea it was, Sans' or Papyrus' or both, but it was an obvious course of action - Papryus needed someone to practise with (on), and Sans was _right here..._

Sans remembers their first time. He hopes Papyrus doesn't.

Sexual battles require an utter callousness towards your opponent's feelings, a willingness to not just _let_ them feel pleasure but _force_ them to. Sexual battles are a rape that forces the victim to enable it.

Sans didn't understand that at first. Sans was pragmatic enough to see it as necessary, Sans didn't share Papyrus' deeper understanding of emotional consequences that made him so reluctant to carry the act out - Sans made the first move, Sans pushed Papyrus into retaliating, Sans taught Papyrus what a sexual battle really is at the same time as he learned it himself.

Sans isn't sure he doesn't hate himself for that. He isn't sure he'll ever understand why Papyrus doesn't.

(It doesn't occur to Sans that Papyrus' first time could have been worse, could have been at the hands (paws, tongue, tail) of someone who didn't care about him at all, who wanted to hurt or break him.

Papyrus has his own pragmatism, and it tells him what Sans did is the gentlest introduction to the truth of sexual battles that he could have had.)

Sans was responsible for their first time, but every time after that has been started by Papyrus. Papyrus has used Sans to learn everything he can think of: how to force sudden, brutal arousal, and how to slowly build it; how to use his tongue, his teeth, to stir another's magic into forming a cock or cunt; how to cause pain through pleasure or pleasure through pain...

Papyrus knows Sans' body better than anyone else in the world. He's more than confident that he can apply those lessons to sexual battles, and Sans is inclined to agree, after far too many times spent quivering in his brother's lap as they watch the televised battles and Papyrus whispers in his earhole about tells and strategies.

(Papyrus has a dream, has had it since he learned it was possible. There are exhibition pairs, monsters who've reached such a plateau that they only fuck their partners instead of 'battling' anyone else (The Royal Couple, Asgore and Toriel) (Dog Marriage, Dogaressa and Dogamy).

Sans could never survive regular battling, but as an exhibition, a submissive masochist with one HP should be very very successful. Papyrus just needs to earn a reputation and use it to find a patron who'll give him - give _them_ \- a chance to prove it.)

 

Sign-ups for the Open Tournaments begin - a grand televised contest, held every other year ("Over 100 participants!" the advertising boasts). Papyrus enters with forged paperwork claiming he's from Snowdin Orphanage, a place with notoriously bad recordkeeping, and hopes that his scarred eye isn't too visible a sign that he's been living on more than humanity's 'charity'.

The clerk gives his clothes an unimpressed look, and sends him to the stores to find something better with the sneer that, "Sexy hobos aren't a thing." He's far from the only monster there, and like most of them, leaves in an outfit composed of so many layers it looks ridiculous.

Officially, participants are only supposed to take one outfit, but no one cares enough to stop them taking more so long as they wear all of it.

 

When the tournament starts, Sans is watching with the other monsters who won't participate in this round. He's still wearing his old sneakers, but now he has thick shorts that reach below his knee, and a fur-lined wine-red coat carefully left unzipped just far enough to reveal a black collar around his neck with a silvery bar engraved TRAINING.

Papyrus, by contrast, is wearing a black tanktop and pleather jeans that cling to his long legs, showing everyone that the temperature doesn't affect him. It turns his scars from marks of shame into cosmetic effects, a display of how 'tough' he is instead of a warning that he's fought - _really_ fought - and survived every time.

"decided to go with the bad-boy look, huh?" Sans mutters, and tries not to think how ridiculously badly it would have gone with his personality when he was younger - because that just leads to thinking about whether it goes with his personality now, and that's something Sans doesn't want to think about.

Papyrus pretends to ignore him, eyelights trained on the arena. Sans isn't sure if he's looking for techniques, or trying to figure out something about his possible future opponents, or what.

He sees the tiniest flinch in Papyrus' expression, and realises he might just be trying to accept what he's gotten himself into. Sans knocks into his shoulder, the closest thing to comfort he can offer.

It's too late to back out now.

 

Papyrus' first opponent is younger than him, blatantly inexperienced in what they should be doing. Papyrus doesn't bother to draw the match out, just pins them, fingers already working the magic at their crotch till they have a wet pussy clenching around his fingers, and brings them off without even undoing his own flies. Sans watches their soul manifest and blaze with the magical aurora of a true orgasm, and tries not to feel jealous that they're the first person other than him to come at Papyrus' hands.

The display earns Papyrus sneers and rolled eyes; no one's impressed with him for failing to put on a show. "What, your stamina's that low you've gotta save it all?" someone jeers, safely anonymous in the mass of people.

Papyrus smirks back, just as unimpressed with them as they are with him, and guides Sans away to a quieter area.

"so, wha-aaa?" Sans' mouth is invaded by Papyrus' tongue before he can finish the question. Habit and training have him pressing back, arms going around his brother's shoulders as he forgets where they are in favour of remembering how good this is.

Papyrus breaks off their kiss as abruptly as he started it. Sans whines, wanting more, but Papyrus just grins at him. "(I'M HARDER FROM KISSING YOU THAN I WAS GETTING THAT IDIOT OFF,)" he says, and Sans flushes as he sees how much tighter Papyrus' jeans have gotten. 

"sorry f'r gettin' jealous, boss," he mumbles.

Papyrus scoffs, "YOU'D BETTER BE. IF YOU CAN'T HANDLE THAT, WHAT ARE YOU GOING TO DO WHEN I PUT EFFORT INTO IT?"

Sans doesn't have an answer. He tries not to think about it as they go to the canteen, as they eat food that they didn't have to steal and don't have to bolt down before someone takes it from them, as they curl up together that night. He tries not to think about Papyrus making another monster come, he tries not to think about another monster making _Papyrus_ come.

He tries not to think about how Papyrus is buying them this comfort with his body. He tries not to think about how easily they could lose it all and be back where they were before starting this.

"DON'T FRET, BROTHER," Papyrus murmurs to him. "THE GREAT PAPYRUS WILL DEFINITIVELY HAVE FOUND A PATRON BY THE TIME HE LEAVES THIS TOURNAMENT." He runs a hand down Sans' spine with intent to soothe, to comfort, instead of to arouse. "I WILL TAKE CARE OF US BOTH, SO LONG AS YOU FOLLOW MY LEAD."

Sans nods against him, and falls asleep.

Papyrus holds his brother close, and reminds himself again of his plan. This tournament to find a patron and build a reputation. A few more to earn the money needed. And then he and Sans can spend the rest of their lives without having to fuck anyone but each other.

It all feels very far away when he thinks about his next match. But Papyrus has no doubt he'll make it.

He dozes off planning what he'll do once he has.


	8. Rimming

**Notes for the Chapter:**

>  _Papyrus/Sans, proto!skelebros, rape shading to dubcon, incest, internalised victim-blaming/slut-shaming, emotionally abusive relationship, bondage, denial, first time_  
>  (Proto!skelebros refers to the very first designs Toby Fox came up with - Papyrus has a fedora, an obsession with My Little Bonies, and no redeeming qualities; Sans works in/owns a casino.)

Sans yanked against the ropes holding him down, still not believing that this was real. "pap, c'mon, bro, quit it -" 

He managed to twist far enough to see his brother's face, and his nonexistent stomach churned. Papyrus wasn't putting on his 'cool' face, the exaggerated sneer he showed other monsters whenever his attempts to be cool led to him doing something he wasn't sure about. Which meant that Papyrus wasn't feeling uncomfortable with what he was doing.

From the look on his face, Sans would say that he was anticipating it - and getting exasperated with Sans. "BROTHER, STOP COMPLAINING! YOU TOLD ME YOURSELF THAT IT DOESN'T MATTER WHAT SLUTS SAY AT FIRST AS LONG AS THEY'RE HAPPY AFTERWARDS. _AND_ THAT IF YOU CAN USE THEM, THEY'RE SLUTS."

Sans cringed, remembering those nights when a more-innocent Papyrus had asked about the girls (and guys) who he kept vanishing off with. Maybe he should have thought through his words a bit more carefully, but he'd just been honest - anyone who'd try to flirt away their losses in a casino had to expect to pay for it, and the same went for those twinks he picked up at the bar. It wasn't as if he'd been cruel with any of them.

"pap, we're _brothers,"_ he tried.

"YES! YOU'LL BE VERY CONVENIENT FOR ME," Papyrus told him, making Sans' eyelights disappear in shock. That - he knew Pap had gotten a bit harsher since he was a kid, but he couldn't be - Sans had to be more than a _convenience_ to him, didn't he?

Papyrus set his bare hands on Sans' equally-bare hips, elegant phalanges rubbing circles into his ilia. His intent pushed heat into Sans' bones, strong enough Sans could practically _hear_ it - **get aroused, make something for me to fuck** \- much too strong for Sans to resist.

(He was used to not resisting Papyrus when the younger wanted something, a half-hearted apology for how often he couldn't be there when what Papyrus needed more than anything was _company.)_

That didn't stop him from trying to struggle away when he felt Papyrus' thumbs spread apart his new-formed ass to reveal his puckered hole, but he couldn't get away as his brother bent over him and huffed, the puff of air on a part he didn't usually have making him jump. "YOU DON'T NEED TO WORRY, BROTHER, I'LL TREAT YOU PROPERLY," Papyrus said, and Sans had a moment to try and pick apart what he'd said - how the fuck did tying him down count as treating Sans properly? Wouldn't "I KNOW WHAT I'M DOING" have been a more normal line? - before Papyrus' tongue pressed against Sans' hole, and Sans lost the ability to think or say more than, "no, no, no, no -"

His brother didn't listen. Sans tried to squirm away, to clench himself shut, to pull himself free of the ropes and his brother's body.

Nothing worked.

Papyrus' tongue was blunt, and wet, and soft, and insistent, and Sans kind of wanted to die at how good it felt as it teased him open, seducing unfamiliar muscles into relaxing for it so it could slip inside him. "stop it," he protested, but Papyrus just kept going, making the resistance melt out of Sans' body. _"please_ stop," he begged, but Papyrus didn't, and Sans' eyelights rolled back at the feeling of his tongue exploring deeper, stroking parts of Sans that didn't normally exist.

Papyrus took his time, diligently working more and more of his tongue into Sans until his older brother was completely lax and reduced to speechless whimpering. Then he started to move it in-and-out, and Sans sobbed as it felt even _better._ He didn't want this, he didn't want to be tongue-fucked by his little brother and he really didn't want it to feel so good, he didn't want to feel himself trying to rock back into each thrust or draw Papyrus' tongue deeper.

He didn't want this, but it was so easy to forget that with all of his magic singing Papyrus' praises. It was so much easier to just give in and let Papyrus take what he wanted.

It felt so much better to just let Papyrus take him.

Neither of them even noticed when Sans' dick formed fully-erect, Papyrus concentrating on driving Sans crazy, Sans too lost in what his brother was doing to him to pay attention to where his pleasure was coming from. Papyrus grunted when he finally spotted the thick shaft, then dragged Sans up slightly to stop him grinding against the table he was bound to and redoubled his efforts to melt Sans' mind with his tongue.

Sans couldn't think, everything focussed on the hot slippery invader making his insides light up in a way he'd never felt before. Words finally came back to him, but all he could say was, "fuck, please, pap, fuck me, please -"

Papyrus' tongue finally slid all the way out, making Sans keen. "I'LL FUCK YOU," he promised as he mounted his brother, and Sans shuddered eagerly as he felt the tip of Papyrus' cock nudge against his empty hole.

 _"yes,"_ he hissed, and then Papyrus was pushing inside him and Sans lost words again to the new aching pleasure of being stretched and overfull of his brother's cock. Papyrus finally untied one of his arms, guiding that hand down underneath him, and Sans willingly stroked himself in time with his brother's thrusts as he was filled and fucked and driven to shuddering, blissful orgasm as his brother's come spattered over the inside of his ribcage.

Sans lay still, afterglow leaving his head full of a warm fuzziness that drowned out any unpleasant thoughts. Papyrus lay over him for a few moments before fumbling to untie him. "SEE, BROTHER? ALL IT TOOK WAS A FEW MINUTES OF MY GREAT TONGUEWORK TO MAKE YOU MY SLUT!" 

The words shook Sans from his daze, leaving him unsure what to think. Sensing his uncertainty, Papyrus scoffed, "YOU AREN'T OBJECTING NOW, ARE YOU?"

Sans felt a shudder of embarrassment, deep enough to almost be shame, work through him at how right Papyrus was. "guess not," he said, turning his face away - he felt weirdly bashful at the moment.

Papyrus retaliated by nipping his scapulum, making him jerk in surprise. "AND NOW YOU KNOW YOU'RE MY SLUT, YOU'LL BE A LOT EASIER NEXT TIME, WON'T YOU?"

The embarrassment sank closer to being shame. "i guess." He'd taught Papyrus this. He couldn't complain about being proven right just because he'd never thought Papyrus might use it on _him._

"DON'T WORRY, BROTHER," Papyrus said, stroking his ribs in a casually-possessive gesture. "I'LL MAKE SURE IT'S JUST AS GOOD FOR YOU _EVERY_ TIME I USE YOU."

"thanks, pap," Sans sighed. The offer warmed him, reassuring him that somewhere in there was the innocent boy who'd learned to hide his true, sweet motives under a shell of selfishness. 

Papyrus _wasn't_ just using him because he was 'convenient'. He was just pretending he was... because Sans had taught him that showing genuine emotions for whoever you were fucking was a chump's game. 

Trust Papyrus to find a way round that. "you're so cool."


	9. Xeno

**Notes for the Chapter:**

> _Sans/Papyrus, speciesswap, flamebros, incest, underage (exact ages unspecified), accidental first time, mutual lack of understanding of what they're doing till afterwards, non-humanlike sex, monsters do not have human cultural values_

The door slammed open. Sans flickered with irritation as his younger brother stomped into the room - Papyrus would be so much easier to deal with if the difference between their ages was larger, but Sans was _just_ older enough to feel like Papyrus should obey him, without being older enough that Pap _would._

"Sanssss!" Pap hissed, red-orange flames shaping themselves to make the word as loud as he could.

"What?" Sans snapped at him, flames already crackling defensively. Most of the time, he was willing to admit that his younger brother was actually pretty cool (as long as said younger brother couldn't hear him), but he'd been looking forwards to having some time to think, and when Papyrus was in the same room he made it difficult to think about anything that wasn't related to him.

"How do we kiss?"

If Sans had eyes, he'd have blinked. As it was, his flames stuttered as he asked in confusion, "What?"

"Cloral said that if you have a datemate you're supposed to kiss them, and -"

"Oh, for -" Sans let his flames roll out, the way other monsters would roll their eyes, "that's just a way of picking on monsters who don't have lips, bro -"

"I know that!" Papyrus snapped, flames billowing. "But monsters who can't _kiss_ -kiss having kissing _things!_ Dog-monsters lick, cat-monsters nuzzle, beaked monsters preen - so what do _we_ do?"

Sans paused, flames drawing together. "Uh."

Sometimes, Papyrus came up with ideas, or ways of looking at things, that Sans would never in a million years have thought of. He really felt like he should have gotten used to it by now, but he still got blindsided on a regular basis.

It didn't help when it felt like something he _should_ have thought of for himself - how _did_ fire elementals display romantic affection to other monsters? It had to be something they wouldn't have to concentrate not to hurt them with, so nuzzling was probably out...

"We should kiss!"

_"What?"_

"We. Should. Kiss! If we practise kissing on each other we'll learn _how_ to kiss, and then when we get datemates we'll be able to kiss _them!"_ Papyrus was bouncing in place with excitement as he explained his idea.

"Huh. Makes sense. Yeah, sure, let's try it," Sans said, twisting around to face him. They leaned in to each other, their flames licking into each other's personal space and slowly starting to merge, Sans' blue with Papyrus' orange. Sans had a vague idea that if they were meant to be kissing, they should probably stop merging - but it felt good, like getting close to his brother, and he was pretty sure that's what kissing was meant to feel like, so he kept going. Papyrus must have agreed, because he was pushing closer, his flames reaching eagerly to merge with Sans' own.

Sans drew back reluctantly, not sure why he was pausing. "You okay, bro?"

Papyrus hissed in the equivalent of a fleshier monster's whimper. "I need - please - my flames aren't hot enough on their own!"

"Me neither," Sans agreed, leaning in with relief that the weird yielding he'd felt in Pap's flames hadn't been him trying to escape without hurting Sans' feelings. 

Confident that he wasn't imagining Pap's flames welcoming his own, Sans pushed further, feeling their merged flames start to flare and ebb in a shaky rhythm, getting warmer and brighter - and his brother felt so good - and warmer and brighter - Papyrus was - was just so - warmer - Sans could feel - brighter - his brother's amazing _soul_ \- hotter - he needed - brighter - they both - they _needed_ \- hotterhotter _brighter_ -

 

The two fire elementals slumped side by side, gasping for air as they slowly came down from the high of burning so fiercely together. "That - that felt -" Papyrus gasped out, satisfied pleasure in every word.

"Fucking _amazing,"_ Sans finished for him, and Papyrus nodded dizzily.

And then Sans had a realisation that felt like a cold wind blowing through him. "Pap - Pap, I think we just _fucked."_

Papyrus' flames flickered with surprise, before he slumped in dejection and groaned, "You mean we _still_ don't know how to kiss?"

Sans felt his flames twist in uneasy amusement. "Don't think so, bro. Pretty sure we just skipped straight over it to land squarely in Fucksville."

Papyrus sighed heavily, leaning against Sans. "And siblings aren't supposed to be datemates unless they're both adults and they've both dated other people and they're living in separate homes and they're both _really really sure_ they want the relationship," he listed.

"Just got that lecture today, huh?" Sans asked, unease dying away to leave the amusement.

"It's what set off Cloral asking other monsters how we kiss," Papyrus explained with a roll of his flames. Then he paused, before saying hesitantly, "And it means we can't - repeat what we just did, doesn't it?"

"It means we _shouldn't,"_ Sans said, not sure if he was agreeing or not. 

Papyrus sighed again. "I _liked_ it. I liked feeling good, and I liked being so close to _you,_ and I liked knowing _you_ were feeling good, and -" he made a point of not looking at Sans - "I _want_ to do it again, and I don't think there's anyone else I'd want to do it _with."_

"Well, we just gotta wait a few more years - and get separate houses - and date other people to be sure we aren't just mixing up familiarity and sex drives with romantic and sexual attraction -"

 _"Or,_ we could just not let people know about it!" Papyrus said with determined cheerfulness.

"Pap -" The words died away before he could speak them. _These laws are meant to protect us._

_Did you even know you could be attracted to me? Because I sure didn't, not before we -_

Papyrus looked at Sans. Not demanding. Not pushy, the way he so often was. Just - hopeful. 

"Brother?" His voice was hushed.

"Yeah, Pap?" Sans whispered, soul fluttering. 

"Kiss me again?"


End file.
